Coatings used in bath and spa applications encounter problems due to the conditions of high humidity that are present in such environments. Some problems associated with coatings used in high humidity environments include water marks, streaks, and defacement issues. Some existing coating products have good water vapor repellency but relatively low water vapor permeability. These products tend to perform well when the coating is relatively fresh; however, when the coating is aged, even just a few months after application, the water vapor permeability can decrease to an undesirable level, weakening the coating's resistance to water vapor condensation. This can then result in some or all of the problems noted above.
Another drawback to existing coatings is found when such products are applied over a previously coated surface. The water repellency of the coatings is weakened by surfactants leached from previous coatings, which can also lead to water marks, streaks, and defacement issues. Existing coatings designed for high humidity applications also tend to be costly.
Silicone resins may offer improved features over the existing coatings; however, they have drawbacks as well. For example, silicone resins tend to be quite costly. Also, they may exhibit poor flow and leveling properties which is undesirable for interior coatings. Problems with recoating may also be present.
An example of an existing coating is Perma-White Mold & Mildew Proof Interior Paint by Zinsser (which is intended to be applied in bath and kitchen areas). This product along with samples of flat paint (ID: JAM0516) and resin paint (ID: EXP-4539) from Dow Chemicals were tested under conditions of high humidity and performed poorly in terms of water vapor condensation resistance. Thus, there is a need for improved coatings for use in high humidity applications.
Prior art formulations differ from the current invention in various ways. For example, the abstract of JP 2008003580 describes a protective film for LCD polarizing plates which comprises a coating layer having a polymer which includes a chlorine containing monomer, which is not part of the present invention. It discloses that the protective film has a water vapor permeability at 60° C. and 95% relative humidity of less than 300 g/m2/day. Further, it fails to teach the water contact angle of the present invention.
The abstract of JP2007047776 describes a display panel that has a polarizing plate with a protective film. It discloses that the ratio of water-vapor permeability of protective film after and before maintaining the display device in a 95% relative humidity environment for 24 hours is 0.003-0.6. Again, it fails to teach the water contact angle of the present invention.
U.S. Pat. No. 3,736,287 describes an aqueous vinyl acrylic interpolymer emulsion and its use in latex paints. The latex paints described are said to provide a high degree of burnish resistance, scrub resistance, ease of stain removal, and low temperature coalescence. There is no mention of water vapor permeability or of a desired water contact angle.
U.S. Pat. No. 5,969,025 is directed to a water-based adhesive composition comprising a blend of adhesive polymers in an aqueous system, wherein the blend of adhesive polymers is: 20-60% by weight of an acrylic polymer having a polarity balance expressed as water absorption according to DIN 53495 of 3 to 20%; and 40-80% by weight of a compatible tackifying resin having a degree of hydrophobicity measured as the contact angle between a dried film of the resin and a drop of distilled water of not less than 60°, the percentages being based on the total of acrylic polymer plus tackifying resin expressed as dry solids. Thus, as noted above, the invention of the '025 patent requires a blend of an acrylic polymer and a tackifying resin, which the present invention does not have.
U.S. Pat. No. 6,114,045 is directed to the films obtained by applying and drying a latex based on special acrylic monomers. These coatings are both flexible and have low surface tack and surface tension. The low tack and hydrophobic nature are provided by the special acrylic monomers. While the coatings are hydrophobic, there is no mention of them being water permeable, and expectations are that they would have poor water permeability. The reference does not disclose the inclusion of a VeoVa monomer or similar monomer, which is included in the present invention.